Distributed wireless power transmission system

ABSTRACT

The embodiments described herein comprise a distributed wireless power transmission system including a plurality of wireless power transmission systems (WPTSs) coordinating transmissions to create a virtual WPTS. The plurality of WPTS coordinate amongst each other to compensate for local phase shift differences between respective clock sources so that transmissions from the WPTSs constructively interfere at a wireless power receiver client (WPRC).

FIELD OF INVENTION

The embodiments described herein comprise a distributed wireless powertransmission system including a plurality of wireless power transmissionsystems (WPTSs) coordinating transmissions to create a virtual WPTS.

BACKGROUND

For a wireless power delivery system including a plurality of wirelesspower transmission systems (WPTSs), a single WPTS can deliver power to awireless power receiver client (WPRC) as the WPRC moves around withinits proximity. Once the WPRC leaves the first WPTS's vicinity, it mustthen receive power from a new WPTS. Disruptions in wireless powerdelivery can occur as the WPRC moves from one WPTS to the next WPTS.

A WPRC may also be located such that it is within the vicinity ofmultiple WPTSs. In this situation, only a single WPTS may be able todeliver wireless power to the WPRC. Alternatively, if multiple WPTSs areable to deliver power to the WPRC, but they are not synchronized acrossthe multiple WPTSs, the wireless power signals from each candestructively interfere with each other, which would result in lesspower delivery than if just a single WPTS wirelessly transmitted power.However, if the multiple WPTSs were able to synchronize theirtransmissions such that the wireless power they transmittedconstructively interfered at the WPRC, they would be able to form avirtual WPTS and deliver significantly more power to the WPRC. Thus, aneed exists for establishing a virtual WPTS comprising multipleindividual WPTSs that transmit power in synchronization to a WPRC.

SUMMARY

Disclosed herein are methods and apparatuses for implementingcoordinated wireless power transmission from multiple wireless powertransmission systems (WPTSs). An example embodiment includes receivingan instruction to group with one or more WPTSs to collaborate totransmit wireless power to a wireless power receiver client (WPRC). Theembodiment may further include receiving an indication of a clockadjusting a phase offset of a local oscillator based on the indicationof the clock. The embodiment may further include providing wirelesspower to the WPRC in collaboration with the one or more WPTSs, whereinthe wireless power is transmitted based on the adjusted phase offset.

Another embodiment may further include forming a virtual WPTS with theone or more WPTSs. The forming may be based on a location of the WPRC.The embodiment may further include receiving an instruction to disbandthe virtual WPTS on a condition that the WPRC has moved away from atleast one of the WPTSs of the one or more WPTSs.

In yet another embodiment, the indication of a clock may indicate aclock from a plurality of clock sources to use as a common clock. In oneexample, the indication of a clock may indicate a central controllerboard clock source.

In yet another embodiment, the WPTS may be a slave WPTS and theinstruction may be received from an elected master WPTS. In one example,the WPTS and the one or more WPTSs may be calibrated with one another toalign transmissions based on respective clocks. In another example, thewireless power provided by the WPRC may substantially constructivelyinterfere at the WPRC with wireless power transmitted by the one or moreWPTSs. In yet another example, the received indication of the clock maybe based on a power received at a calibration unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a system diagram including an example wireless powertransmission environment.

FIG. 2 is a block diagram illustrating example components of an exampleembodiment of a wireless power transmission system (WPTS).

FIG. 3 is a block diagram illustrating an example embodiment of a WPRC.

FIG. 4 is a diagram illustrating an example embodiment of a wirelesssignal delivery environment.

FIGS. 5A and 5B are diagrams of an example system of multiple wirelesspower transmission systems (WPTSs) and a wireless power receiver client(WPRC).

FIGS. 6A, 6B, and 6C are diagrams of example topologies in which acommon clock source may be shared in a multiple WPTS system.

FIG. 7 is a diagram depicting an example method of a system of multipleWPTSs implementing features of a virtual WPTS.

FIG. 8 is a diagram depicting an example system for calibrating anantenna for synchronized transmission with other antennas in the system.

FIG. 9 is a signal flow diagram depicting an example system includingtwo WPTSs that are calibrated to act as a virtual WPTS to providewireless power to a WPRC.

FIG. 10 is a signal flow diagram depicting another example systemincluding two WPTSs that are calibrated to act as a virtual WPTS toprovide wireless power to a WPRC.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a system diagram including an example wireless powertransmission environment 100 illustrating wireless power delivery fromone or more wireless power transmission systems (WPTSs), such as WPTS101. More specifically, FIG. 1 illustrates power transmission to one ormore wireless power receiver clients (WPRCs) 110 a-110 c. WPTS 101 maybe configured to receive encoded beacons 111 a-111 c from and transmitwireless power 112 a-112 c and wireless data 113 a-113 c to WPRCs 110a-110 c. WPRCs 110 a-110 c may be configured to receive and processwireless power 112 a-112 c from one or more WPTSs, such as WPTS 101.Components of an example WPTS 101 are shown and discussed in greaterdetail below, as well as in FIG. 2. Components of an example WPRC 110a-110 c are shown and discussed in greater detail with reference to FIG.3.

WPTS 101 may include multiple antennas 103 a-103 n, e.g., an antennaarray including a plurality of antennas, which may be capable ofdelivering wireless power 112 a-112 c to WPRCs 110 a-110 c. In someembodiments, the antennas are adaptively-phased radio frequency (RF)antennas. The WPTS 101 may be capable of determining the appropriatephases with which to deliver a coherent power transmission signal toWPRCs 110 a-110 c. Each antenna of the antenna array including antennas103 a-103 n may be configured to emit a signal, e.g. a continuous waveor pulsed power transmission signal, at a specific phase relative toeach other antenna, such that a coherent sum of the signals transmittedfrom a collection of the antennas is focused at a location of arespective WPRC 110 a-110 c. Although FIG. 1 depicts wireless signalsincluding encoded beacon signals 111 a-111 c, wireless powertransmission 112 a-112 c, and wireless data 113 a-113 c each beingtransmitted by or received by a single antenna of the antennas 103 a-103n of the WPTS 101, this should not be construed as limiting in any way.Any number of antennas may be employed in the reception and transmissionof signals. Multiple antennas, including a portion of antennas 103 a-103n that may include all of antennas 103 a-103 n, may be employed in thetransmission and/or reception of wireless signals. It is appreciatedthat use of the term “array” does not necessarily limit the antennaarray to any specific array structure. That is, the antenna array doesnot need to be structured in a specific “array” form or geometry.Furthermore, as used herein the term “array” or “array system” may beused include related and peripheral circuitry for signal generation,reception and transmission, such as radios, digital circuits and modems.

As illustrated in the example of FIG. 1, antennas 103 a-103 n may beincluded in WPTS 101 and may be configured to transmit both power anddata and to receive data. The antennas 103 a-103 n may be configured toprovide delivery of wireless radio frequency power in a wireless powertransmission environment 100, to provide data transmission, and toreceive wireless data transmitted by WPRCs 110 a-110 c, includingencoded beacon signals 111 a-111 c. In some embodiments, the datatransmission may be through lower power signaling than the wirelessradio frequency power transmission. In some embodiments, one or more ofthe antennas 103 a-103 n may be alternatively configured for datacommunications in lieu of wireless power delivery. In some embodiments,one or more of the power delivery antennas 103 a-103 n can alternativelyor additionally be configured for data communications in addition to orin lieu of wireless power delivery. The one or more data communicationantennas are configured to send data communications to and receive datacommunications from WPRCs 110 a-110 c.

Each of WPRCs 110 a-110 c may include one or more antennas (not shown)for transmitting signals to and receiving signals from WPTS 101.Likewise, WPTS 101 may include an antenna array having one or moreantennas and/or sets of antennas, each antenna or set of antennas beingcapable of emitting continuous wave or discrete (pulse) signals atspecific phases relative to each other antenna or set of antennas. Asdiscussed above, WPTSs 101 is capable of determining the appropriatephases for delivering the coherent signals to the antennas 103 a-103 n.For example, in some embodiments, delivering coherent signals to aparticular WPRC can be determined by computing the complex conjugate ofa received encoded beacon signal at each antenna of the array or eachantenna of a portion of the array such that a signal from each antennais phased appropriately relative to a signal from other antennasemployed in delivering power or data to the particular WPRC thattransmitted the beacon signal. The WPTS 101 can be configured to emit asignal (e.g., continuous wave or pulsed transmission signal) frommultiple antennas using multiple waveguides at a specific phase relativeto each other. Other techniques for delivering a coherent wireless powersignal are also applicable such as, for example, the techniquesdiscussed in U.S. patent application Ser. No. 15/852,216 titled “AnytimeBeaconing In A WPTS” filed Dec. 22, 2017 and in U.S. patent applicationSer. No. 15/852,348 titled “Transmission Path Identification based onPropagation Channel Diversity” filed Dec. 22, 2017; which are expresslyincorporated by reference herein.

Although not illustrated, each component of the wireless powertransmission environment 100, e.g., WPRCs 110 a-110 c, WPTS 101, caninclude control and synchronization mechanisms, e.g., a datacommunication synchronization module. WPTS 101 can be connected to apower source such as, for example, a power outlet or source connectingthe WPTSs to a standard or primary alternating current (AC) power supplyin a building. Alternatively, or additionally, WPTS 101 can be poweredby a battery or via other mechanisms, e.g., solar cells, etc.

As shown in the example of FIG. 1, WPRCs 110 a-110 c include mobilephone devices and a wireless tablet. However, WPRCs 110 a-110 c can beany device or system that needs power and is capable of receivingwireless power via one or more integrated WPRCs. Although three WPRCs110 a-110 c are depicted, any number of WPRCs may be supported. Asdiscussed herein, a WPRC may include one or more integrated powerreceivers configured to receive and process power from one or more WPTSsand provide the power to the WPRCs 110 a-110 c or to internal batteriesof the WPRCs 110 a-110 c for operation thereof.

As described herein, each of the WPRCs 110 a-110 c can be any systemand/or device, and/or any combination of devices/systems that canestablish a connection with another device, a server and/or othersystems within the example wireless power transmission environment 100.In some embodiments, the WPRCs 110 a-110 c may each include displays orother output functionalities to present or transmit data to a userand/or input functionalities to receive data from the user. By way ofexample, WPRC 110 a can be, but is not limited to, a video gamecontroller, a server desktop, a desktop computer, a computer cluster, amobile computing device such as a notebook, a laptop computer, ahandheld computer, a mobile phone, a smart phone, a PDA, a Blackberrydevice, a Treo, and/or an iPhone, etc. By way of example and notlimitation, WPRC 110 a can also be any wearable device such as watches,necklaces, rings or even devices embedded on or within the customer.Other examples of WPRC 110 a include, but are not limited to, a safetysensor, e.g. a fire or carbon monoxide sensor, an electric toothbrush,an electronic door lock/handle, an electric light switch controller, anelectric shaver, an electronic shelf label (ESL), etc.

Although not illustrated in the example of FIG. 1, the WPTS 101 and theWPRCs 110 a-110 c can each include a data communication module forcommunication via a data channel. Alternatively, or additionally, theWPRCs 110 a-110 c can direct antennas to communicate with WPTS 101 viaexisting data communications modules. In some embodiments, the WPTS 101can have an embedded Wi-Fi hub for data communications via one or moreantennas or transceivers. In some embodiments, the antennas 103 a-103 ncan communicate via Bluetooth™, Wi-Fi™, ZigBee™, etc. The WPRCs 110a-110 c may also include an embedded Bluetooth™, Wi-Fi™, ZigBee™, etc.transceiver for communicating with the WPTS 101. Other datacommunication protocols are also possible. In some embodiments thebeacon signal, which is primarily referred to herein as a continuouswaveform, can alternatively or additionally take the form of a modulatedsignal and/or a discrete/pulsed signal.

WPTS 101 may also include control circuit 102. Control circuit 102 maybe configured to provide control and intelligence to the WPTS 101components. Control circuit 102 may comprise one or more processors,memory units, etc., and may direct and control the various data andpower communications. Control circuit 102 may direct data communicationson a data carrier frequency that may be the same or different than thefrequency via which wireless power is delivered. Likewise, controlcircuit 102 can direct wireless transmission system 100 to communicatewith WPRCs 110 a-110 c as discussed herein. The data communications canbe, by way of example and not limitation, Bluetooth™, Wi-Fi™, ZigBee™,etc. Other communication protocols are possible.

It is appreciated that the use of the term “WPTS” does not necessarilylimit the WPTS to any specific structure. That is, the WPTS does notneed to be structured in a specific form or geometry. Furthermore, asused herein the term “transmission system” or “WPTS” may be used toinclude related and peripheral circuitry for signal generation,reception and transmission, such as radios, digital circuits and modems.

FIG. 2 is a block diagram illustrating example components of a WPTS 200in accordance with the embodiments described herein. As illustrated inthe example of FIG. 2, the WPTS 200 may include a control circuit 201,external power interface 202, and power system 203. Control circuit 201may include processor 204, for example a base band processor, and memory205. Additionally, although only one antenna array board 208 and onetransmitter 206 are depicted in FIG. 2, WPTS 200 may include one or moretransmitters 206 coupled to one or more antenna array boards 208 andtransmit signals to the one or more antenna array boards 208. Althoughonly one receiver is depicted in FIG. 2, one or more receivers 207 maybe coupled to the one or more antenna array boards 208 and may receivesignals from the one or more antennas 250 a-250 n of the one or moreantenna array boards 208. Each antenna array board 208 includes switches220 a-220 n, phase shifters 230 a-230 n, power amplifiers 240 a-240 n,and antenna arrays 250 a-250 n. Although each switch, phase shifter,power amplifier, and antenna is depicted in a one-to-one relationship,this should not be construed as limiting. Additionally or alternatively,any number of switches, phase shifters, power amplifiers, and antennasmay be coupled. Some or all of the components of the WPTS 200 can beomitted, combined, or sub-divided in some embodiments. Furthermore, thesetting of the switches 220 a-220 n and phase shifters 230 a-230 nshould not be construed as limiting. Any of the switches 220 a-220 n,phase shifters 230 a-230 n, and/or power amplifiers 240 a-240 n, or anycombination thereof, may be individually controlled or controlled ingroups. The signals transmitted and received by the one or more antennaarray boards 208 may be wireless power signals, wireless data signals,or both.

Control circuit 201 is configured to provide control and intelligence tothe array components including the switches 220 a-220 n, phase shifters230 a-230 n, power amplifiers 240 a-240 n, and antenna arrays 250 a-250n. Control circuit 201 may direct and control the various data and powercommunications. Transmitter 206 can generate a signal comprising poweror data communications on a carrier frequency. The signal can be complywith a standardized format such as Bluetooth™, Wi-Fi™, ZigBee™, etc.,including combinations or variations thereof. Additionally oralternatively, the signal can be a proprietary format that does not useBluetooth™, Wi-Fi™, ZigBee™, and the like, and utilizes the sameswitches 220 a-220 n, phase shifters 230 a-230 n, power amplifiers 240a-240 n, and antenna arrays 250 a-250 n to transmit wireless data as areused to transmit wireless power. Such a configuration may save onhardware complexity and conserve power by operating independently of theconstraints imposed by compliance with the aforementioned standardizedformats. In some embodiments, control circuit 201 can also determine atransmission configuration comprising a directional transmission throughthe control of the switches 220 a-220 n, phase shifters 230 a-230 n, andamplifiers 240 a-240 n based on an encoded beacon signal received from aWPRC 210.

The external power interface 202 is configured to receive external powerand provide the power to various components. In some embodiments, theexternal power interface 202 may be configured to receive, for example,a standard external 24 Volt power supply. In other embodiments, theexternal power interface 202 can be, for example, 120/240 Volt AC mainsto an embedded DC power supply which may source, for example, 12/24/48Volt DC to provide the power to various components. Alternatively, theexternal power interface could be a DC supply which may source, forexample, 12/24/48 Volts DC. Alternative configurations including othervoltages are also possible.

Switches 220 a-220 n may be activated to transmit power and/or data andreceive encoded beacon signals based on the state of the switches 220a-220 n. In one example, switches 220 a-220 n may be activated, e.g.closed, or deactivated, e.g. open, for power transmission, datatransmission, and/or encoded beacon reception. Additional components arealso possible. For example, in some embodiments phase-shifters 230 a-230n may be included to change the phase of a signal when transmittingpower or data to a WPRC 210. Phase shifter 230 a-230 n may transmit apower or data signal to WPRC 210 based on a phase of a complex conjugateof the encoded beaconing signal from WPRC 210. The phase-shift may alsobe determined by processing the encoded beaconing signal received fromWPRC 210 and identifying WPRC 210. WPTS 200 may then determine aphase-shift associated with WPRC 210 to transmit the power signal. In anexample embodiment, data transmitted from the WPTS 200 may be in theform of communication beacons which may be used to synchronize clockswith WPRC 210. This synchronization may improve the reliability ofbeacon phase detection.

In operation, control circuit 201, which may control the WPTS 200, mayreceive power from a power source over external power interface 202 andmay be activated. Control circuit 201 may identify an available WPRC 210within range of the WPTS 200 by receiving an encoded beacon signalinitiated by the WPRC 210 via at least a portion of antennas 250 a-250n. When the WPRC 210 is identified based on the encoded beacon signal, aset of antenna elements on the WPTS may power on, enumerate, andcalibrate for wireless power and/or data transmission. At this point,control circuit 201 may also be able to simultaneously receiveadditional encoded beacon signals from other WPRCs via at least aportion of antennas 250 a-250 n.

Once the transmission configuration has been generated and instructionshave been received from control circuit 201, transmitter 206 maygenerate and transfer one or more power and/or data signal waves to oneor more antenna boards 208. Based on the instruction and generatedsignals, at least a portion of power switches 220 a-220 n may be openedor closed and at least a portion of phase shifters 230 a-230 n may beset to the appropriate phase associated with the transmissionconfiguration. The power and/or data signal may then be amplified by atleast a portion of power amplifiers 240 a-240 n and transmitted at anangle directed toward a location of WPRC 210. As discussed herein, atleast a portion of antennas 250 a-250 n may be simultaneously receivingencoded beacon signals from additional WPRCs 210.

As described above, a WPTS 200 may include one or more antenna arrayboards 208. In one embodiment, each antenna array board 208 may beconfigured to communicate with a single WPRC 210, so that a differentantenna array board 208 of a plurality of antenna array boards 208communicates with a different WPRC 210 of a plurality of WPRCs 210. Suchan implementation may remove a reliance on a communication method, suchas a low-rate personal area network (LR-WPAN), IEEE 802.15.4, orBluetooth Low Energy (BLE) connection to synchronize with a WPRC 210. AWPTS 200 may receive a same message from a WPRC 210 via differentantennas of antennas 250 a-250 n. The WPTS 200 may use the replicationof the same message across the different antennas to establish a morereliable communication link. In such a scenario, a beacon power may belowered since the lower power can be compensated by the improvedreliability owed to the replicated received signals. In someembodiments, it may also be possible to dedicate certain antennas orgroups of antennas for data communication and dedicate other antennas orgroups of antennas for power delivery. For example, an example WPTS 200may dedicate 8 or 16 antennas of antennas 250 a-250 n to datacommunication at a lower power level than some number of remainingantennas that may be dedicated to power delivery at a relatively higherpower level than the data communication.

FIG. 3 is a block diagram illustrating an example WPRC 300 in accordancewith embodiments described herein. As shown in the example of FIG. 3,WPRC 300 may include control circuit 301, battery 302, a control module303, for example an Internet of Things (IoT) control module,communication block 306 and associated one or more antennas 320, powermeter 309, rectifier 310, a combiner 311, beacon signal generator 307,beacon coding unit 308 and associated one or more antennas 321, andswitch 312 connecting the combiner 311 or the beacon signal generator307 to one or more associated antennas 322 a-322 n. The battery 302 mayalternatively be replaced by a capacitor. Although not depicted, theWPRC 300 may include an energy harvesting circuit which may enable theWPRC 300 to operate with a capacitor for short term energy storageinstead of or in addition to using the battery. Some or all of thedepicted components in FIG. 3 can be omitted, combined, or sub-dividedin some embodiments. Some or all of the components depicted in FIG. 3may be incorporated in a single integrated chip (IC). It should be notedthat although the WPTS 200 may use full-duplexing, WPRC 300 mayadditionally or alternatively use half-duplexing. A received and/ortransmitted data rate may be, for example, 20 Mbps. However, higher orlower data rates may be implemented to achieve other design goals. TheWPRC 300 may transmit acknowledgement (ACK) messages back to a WPTS,such as a WPTS 200 depicted in FIG. 2. Although not depicted, a localCPU may be incorporated into WPRC 300. For example, the local CPU may beincluded in the control circuit 301.

A combiner 311 may receive and combine the received power and/or datatransmission signals received via one or more antennas 322 a-322 n. Thecombiner can be any combiner or divider circuit that is configured toachieve isolation between output ports while maintaining a matchedcondition. For example, the combiner 311 can be a Wilkinson PowerDivider circuit. The combiner 311 may be used to combine two or more RFsignals while maintaining a characteristic impedance, for example, 50ohms. The combiner 311 may be a resistive-type combiner, which usesresistors, or a hybrid-type combiner, which uses transformers. Therectifier 310 may receive the combined power transmission signal fromthe combiner 311, if present, which may be fed through the power meter309 to the battery 302 for charging. In other embodiments, eachantenna's power path can have its own rectifier 310 and the DC power outof the rectifiers is combined prior to feeding the power meter 309. Thepower meter 309 may measure the received power signal strength and mayprovide the control circuit 301 with this measurement.

Battery 302 may include protection circuitry and/or monitoringfunctions. Additionally, the battery 302 may include one or morefeatures, including, but not limited to, current limiting, temperatureprotection, over/under voltage alerts and protection, and batterycapacity monitoring, for example coulomb monitoring. The control circuit301 may receive the battery power level from the battery 302 itself. Asindicated above, although not shown, a capacitor may be substituted forthe battery 302 or may be implemented in addition to the battery 302.The control circuit 301 may also transmit/receive via the communicationblock 306 a data signal on a data carrier frequency, such as the basesignal clock for clock synchronization. The beacon signal generator 307may generate the beacon signal or calibration signal and may transmitthe beacon signal or calibration signal using one or more antennas 321.

It may be noted that, although the battery 302 is shown as charged by,and providing power to, WPRC 300, the receiver may also receive itspower directly from the rectifier 310. This may be in addition to therectifier 310 providing charging current to the battery 302, or in lieuof providing charging. Also, it may be noted that the use of multipleantennas 320, 321, and 322 a-322 n is one example of implementation,however the structure may be reduced to one shared antenna.

In some embodiments, the control circuit 301 and/or the control module303 can communicate with and/or otherwise derive device information fromWPRC 300. The device information can include, but is not limited to,information about the capabilities of the WPRC 300, usage information ofthe WPRC 300, power levels of the battery or batteries 302 of the WPRC300, and/or information obtained or inferred by the WPRC 300. In someembodiments, a client identifier (ID) module 305 stores a client ID thatcan uniquely identify the WPRC 300 in a wireless power deliveryenvironment. For example, the ID can be transmitted to one or more WPTSsin the encoded beacon signal. In some embodiments, WPRCs may also beable to receive and identify other WPRCs in a wireless power deliveryenvironment based on the client ID.

A motion sensor 304 can detect motion and may signal the control circuit301 to act accordingly. For example, a device receiving power mayintegrate motion detection mechanisms such as accelerometers orequivalent mechanisms to detect motion. Once the device detects that itis in motion, it may be assumed that it is being handled by a user, andmay trigger a signal to the antenna array of the WPTS to either stoptransmitting power and/or data, or to initiate wireless power and/ordata transmission from the WPTS. The WPRC may use the encoded beacon orother signaling to communicate with the WPTS. In some embodiments, whena WPRC 300 is used in a moving environment like a car, train or plane,the power might only be transmitted intermittently or at a reduced levelunless the WPRC 300 is critically low on power.

FIG. 4 is a diagram illustrating an example wireless signal deliveryenvironment 400 in accordance with embodiments described herein. Thewireless signal delivery environment 400 includes WPTS 401, a useroperating WPRCs 402 a and 402 b, and wireless network 409. Although twoWPRCs are depicted in FIG. 4, any number of WPRCs may be supported. WPTS401 as depicted in FIG. 4 can alternatively be implemented in accordancewith WPTS 101 as depicted in FIG. 1. Alternative configurations are alsopossible. Likewise, WPRCs 402 a and 402 b as depicted in FIG. 4 can beimplemented in accordance with WPRCs 110 a-110 c of FIG. 1, or can beimplemented in accordance with WPRC 300 as depicted in FIG. 3, althoughalternative configurations are also possible.

WPTS 401 may include a power supply 403, memory 404, processor 405,interface 406, one or more antennas 407, and a networking interfacedevice 408. Some or all of the components of the WPTS 401 can beomitted, combined, or sub-divided in some embodiments. The networkinginterface device may communicate wired or wirelessly with a network 409to exchange information that may ultimately be communicated to or fromWPRCs 402 a and 402 b. The one or more antennas 407 may also include oneor more receivers, transmitters, and/or transceivers. The one or moreantennas 407 may have a radiation and reception pattern directed in aspace proximate to WPRC 402 a, WPRC 402 b, or both, as appropriate. WPTS401 may transmit a wireless power signal, wireless data signal, or bothover at least a portion of antennas 407 to WPRCs 402 a and 402 b. Asdiscussed herein, WPTS 401 may transmit the wireless power signal,wireless data signal, or both at an angle in the direction of WPRCs 402a and 402 b such that the strength of the respectively received wirelesssignal by WPRCs 402 a and 402 b depends on the accuracy of thedirectivity of the corresponding directed transmission beams from atleast a portion of antennas 407.

A fundamental property of antennas is that the receiving pattern of anantenna when used for receiving is directly related to the far-fieldradiation pattern of the antenna when used for transmitting. This is aconsequence of the reciprocity theorem in electromagnetics. Theradiation pattern can be any number of shapes and strengths depending onthe directivity of the beam created by the waveform characteristics andthe types of antennas used in the antenna design of the antennas 407.The types of antennas 407 may include, for example, horn antennas,simple vertical antenna, etc. The antenna radiation pattern can compriseany number of different antenna radiation patterns, including variousdirective patterns, in a wireless signal delivery environment 400. Byway of example and not limitation, wireless power transmitcharacteristics can include phase settings for each antenna and/ortransceiver, transmission power settings for each antenna and/ortransceiver, or any combination of groups of antennas and transceivers,etc.

As described herein, the WPTS 401 may determine wireless communicationtransmit characteristics such that, once the antennas and/ortransceivers are configured, the multiple antennas and/or transceiversare operable to transmit a wireless power signal and/or wireless datasignal that matches the WPRC radiation pattern in the space proximate tothe WPRC. Advantageously, as discussed herein, the wireless signal,including a power signal, data signal, or both, may be adjusted to moreaccurately direct the beam of the wireless signal toward a location of arespective WPRC, such as WPRCs 402 a and 402 b as depicted in FIG. 4.

The directivity of the radiation pattern shown in the example of FIG. 4is illustrated for simplicity. It is appreciated that any number ofpaths can be utilized for transmitting the wireless signal to WPRCs 402a and 402 b depending on, among other factors, reflective and absorptiveobjects in the wireless communication delivery environment. FIG. 4depicts direct signal paths, however other signal paths, includingmulti-path signals, that are not direct are also possible.

The positioning and repositioning of WPRCs 402 a and 402 b in thewireless communication delivery environment may be tracked by WPTS 401using a three-dimensional angle of incidence of an RF signal at anypolarity paired with a distance that may be determined by using an RFsignal strength or any other method. As discussed herein, an array ofantennas 407 capable of measuring phase may be used to detect awave-front angle of incidence. A respective angle of direction towardWPRCs 402 a and 402 b may be determined based on respective distance toWPRCs 402 a and 402 b and on respective power calculations.Alternatively, or additionally, the respective angle of direction toWPRCs 402 a and 402 b can be determined from multiple antenna arraysegments 407.

In some embodiments, the degree of accuracy in determining therespective angle of direction toward WPRCs 402 a and 402 b may depend onthe size and number of antennas 407, number of phase steps, method ofphase detection, accuracy of distance measurement method, RF noise levelin environment, etc. In some embodiments, users may be asked to agree toa privacy policy defined by an administrator for tracking their locationand movements within the environment. Furthermore, in some embodiments,the system can use the location information to modify the flow ofinformation between devices and optimize the environment. Additionally,the system can track historical wireless device location information anddevelop movement pattern information, profile information, andpreference information.

Disclosed herein are embodiments of a system and method for coordinatingmultiple WPTSs to act as a single, virtual WPTS to provide wirelesspower to one or more WPRCs. Such a virtual WPTS may exhibit a largervirtual aperture than any single WPTS. By coordinating transmissionsfrom multiple WPTSs, a virtual WPTS can be dynamically formed from anoptimal selection of WPTSs to wirelessly transmit power to a WPRC in acoordinated fashion such that their respective transmissionsconstructively interfere at a location of the WPRC to deliversignificantly greater power than any single WPTS and significantlygreater power than the same collection of WPTSs without havingcoordinated transmissions.

FIG. 5A is a diagram depicting an example system 500A of four WPTSs 1-4and a single WPRC 550A. As depicted in FIG. 5A, WPRC 550A may be locatedproximate to WPTS 1 and WPTS 2. Based on a determined location of WPRC550A, WPTS 1 and WPTS 2 may be selected to be grouped as a virtual WPTS560A to transmit wireless power to WPRC 550A. For example, WPRC 550A maytransmit a beacon that is received by WPTS 1 and WPTS 2 and may not bereceived or weakly received by WPTS 3 and WPTS 4. Alternatively, WPTS 3and WPTS 4 may not be selected based on reasons that are not locationbased. For example, WPTS 3 and WPTS 4 may be heavily loaded with otherwireless power demands and at least based on their load they may beexcluded from the virtual WPTS 560A. Location of the WPRC influencinghow WPTSs group together is meant to be exemplary only. Any examples ofa reason for joining a group of WPTSs and excluding other WPTSs is notmeant to be limiting. Any number of reasons may cause a plurality ofWPTSs to group together to form a virtual WPTS.

WPTS 1 and WPTS 2 may share a common clock to adjust respective phase oftheir transmissions so that the phases of their wireless powertransmissions align at the location of the WPRC 550A and hence theirtransmissions constructively interfere at the WPRC 550A. As depicted inFIG. 5A, each of WPTS 1 and WPTS 2 may include a clock source 510A and520A, respectively. Either clock source may be used as the common clocksource and shared with the other WPTS. Alternatively, although notshown, WPTS 1 and WPTS 2 may be controlled by a central controller board(CCB) which may include a clock source that is shared with WPTS 1 andWPTS 2 to coordinate their transmissions. Once phases of WPTS 1 and/orWPTS 2 are properly adjusted with respect to each other, wireless power501A from WPTS 1 and wireless power 502A from WPTS 2 may be delivered toWPRC 550A.

FIG. 5B is a diagram depicting an example system 500B of four WPTSs 1-4and a single WPRC 550B. As depicted in FIG. 5B, WPRC 550B may have movedfrom its location depicted in FIG. 5A such that it is now locatedproximate to WPTS 2, WPTS 3 and WPTS 4. As WPRC 550B moved away fromWPTS 560A depicted in FIG. 5A, virtual WPTS 560A may be disbanded as itmay no longer be optimal for providing wireless power to WPRC 550B.Again, by way of example, a determined location of WPRC 550B may be usedfor making a determination to disband. Similarly, using a determinedlocation of WPRC 550B, WPTS 2, WPTS 3, and WPTS 4 may be selected to begrouped as a virtual WPTS 560B to transmit wireless power to WPRC 550B.By way of example, WPRC 550B may transmit a beacon that is received byWPTS 2, WPTS 3, and WPTS 4 and may not be received or weakly received byWPTS 1. Alternatively, WPTS 1 may not be selected based on reasons thatare not location based. For example, WPTS 1 may be heavily loaded withother wireless power demands and at least based on its load it may beexcluded from the virtual WPTS 560B.

WPTS 2, WPTS 3, and WPTS 4 may share a common clock to adjust respectivephases of their transmissions so that the phases of their wireless powertransmissions align at the location of the WPRC 550B so that theirtransmissions constructively interfere at the WPRC 550B. As depicted inFIG. 5B, each of WPTS 2, WPTS 3, and WPTS 4 may include a clock source520B, 530B, and 540B, respectively. Any of said clock sources may beused as the common clock source and shared with the other WPTSs.Alternatively, although not shown, WPTS 2, WPTS 3, and WPTS 4 may becontrolled by a CCB which may include a clock source that is shared withWPTS 2, WPTS 3, and WPTS 4 to coordinate their transmissions. Oncephases of WPTS 2, WPTS 3, and/or WPTS 4 are properly adjusted withrespect to each other, wireless power 502B from WPTS 2, wireless power503B from WPTS 3, and wireless power 504B from WPTS 4 may be deliveredto WPRC 550B.

Although FIGS. 5A and 5B depict an example system in two dimensions, itshould be understood that a system of WPTSs may be arranged in threedimensions and a WPRC may move in three dimensions. Like the depictionsin FIGS. 5A and 5B, appropriate WPTSs may be dynamically selected anddeselected to form and disband virtual WPTSs in three dimensional spaceto provide wireless power to a WPRC as it moves in three dimensions.Furthermore, the number of WPTSs is purely by way of example. More orfewer WPTSs may be implemented. Likewise, although WPRC 550A/550B isdepicted as receiving wireless power from two WPTSs and then three WPTSsin FIG. 5A and FIG. 5B, respectively, any number of WPTSs may deliverwireless power to WPRC 550A/550B. Additionally, although only one WPRC550A/550B is depicted, the collection of WPTSs can service any number ofWPRCs concurrently using appropriate scheduling and can form a virtualWPTS for each respective WPRC.

FIGS. 6A, 6B, and 6C are diagrams depicting example topologies in whicha common clock source may be shared in a multiple WPTS system. Althoughonly two WPTSs are depicted in FIGS. 6A, 6B, and 6C, this is notlimiting. Any number of WPTSs may share a common clock.

FIG. 6A depicts a CCB 690A that may be connected to WPTS 1 viaconnection 610A. CCB 690A may be connected to WPTS 2 via connection620A. A clock source 609A may be included in CCB 690A and may be sharedwith WPTS 1 and WPTS 2 via connections 610A and 620A, respectively. Theconnections 610A and 620A may be a wired connection or a fiber opticconnection, for example. WPTS 1 and WPTS 2 may exchange signals with CCB690A to establish a common clock and respective phase offsets for WPTS 1and WPTS 2 such that their wireless power transmissions may be timealigned.

FIG. 6B depicts a CCB 690B that may be connected to WPTS 1 via awireless connection 610B. CCB 690B may be connected to WPTS 2 via awireless connection 620B. A clock source 609B may be included in CCB690B and may be shared with WPTS 1 and WPTS 2 via wireless connections610B and 620B, respectively. The wireless connections 610B and 620B maybe on a same frequency as wireless power transmissions or may be on adifferent frequency. Additionally, WPTS 1 and WPTS 2 may communicatewith CCB 690B via the same antennas or a portion of the same antennasvia which WPTS 1 and WPTS 2 transmit wireless power to a WPRC.Additionally or alternatively, WPTS 1 and WPTS 2 may use one or moredifferent antennas that may be configured for communication with CCB690B. WPTS 1 and WPTS 2 may exchange signals with CCB 690B to establisha common clock and respective phase offsets for WPTS 1 and WPTS 2 suchthat their wireless power transmissions may be time aligned.

FIG. 6C depicts WPTS 1 and WPTS 2 that may share a clock signal via awireless connection 612C. Alternatively, although not shown, a wiredconnection between WPTS 1 and WPTS 2 may be used to share the clocksignal. A clock source 601C may be included in WPTS 1 may be shared withWPTS 2 and/or a clock source 602C may be included in WPTS 2 and may beshared with WPTS 1 via wireless connection 612C. The wireless connection612C may be on a same frequency as wireless power transmissions or maybe on a different frequency. Additionally, WPTS 1 and WPTS 2 maycommunicate with each other via the same antennas or a portion of thesame antennas via which WPTS 1 and WPTS 2 transmit wireless power to aWPRC. Additionally or alternatively, WPTS 1 and WPTS 2 may use one ormore different antennas that may be configured for communication witheach other. WPTS 1 and WPTS 2 may exchange signals with each other toestablish a common clock and respective phase offsets for WPTS 1 andWPTS 2 such that their wireless power transmissions may be time aligned.

FIG. 7 is a diagram depicting an example method 700 of a system ofmultiple WPTSs implementing features of a virtual WPTS in accordancewith the teachings herein. At 710, it may be determined which WPTSsshould collaborate to form a virtual WPTS. Such a determination may bemade by a CCB and/or by one or more of the WPTSs. For example, each WPTSmay independently determine that it is well-suited to power a WPRC andmay transmit a signal to nearby WPTSs that it should be paired with theWPRC to provide wireless power to the WPRC. A predicted power may beused to determine whether a WPTS may be well-suited to be a part of avirtual WPTS to provide power to the WPRC. Additionally oralternatively, a WPTS may run a test with the WPRC to determine how muchpower transmitted by the WPTS may be received by the WPRC to thendetermine how well-suited the WPTS is for pairing with the WPRC. Forexample, all WPTSs over some selected power delivery threshold may bejoined together to form the virtual WPTS. The candidate WPTSs may alsoexchange signaling to identify and acknowledge the determined group ofWPTSs that will form the virtual WPTS.

At 720, it may be determined which clock source will be shared with allWPTSs in the virtual WPTS. One or more CCBs may be connected to thegroup of WPTSs forming the virtual WPTS. A clock source from one of theCCBs may be used and shared with the group of WPTSs. Alternatively, eachWPTS of the group of WPTSs may include a clock source. A WPTS may shareits clock source to use as a common clock source with the other WPTSs inthe group of the WPTSs. The clock source may be used to adjust clockphases of each WPTS appropriately such that their respectivetransmissions constructively interfere at a location of the WPRC. At730, the selected clock source may be shared with all WPTSs in thevirtual WPTS. The selected clock source may be shared via a wired orwireless connection.

At 740, a WPTS of the group of WPTSs forming the virtual WPTS may beelected as the master WPTS to use for calibration of the WPTSs. Althoughthe master WPTS is elected at 740 in FIG. 7, this particular order isnot limiting. The master WPTS may be elected at any time. For example,the WPTS may be elected at 720 and the master WPTS may be used as theclock source to be shared with the other WPTSs or the master WPTS mayselect another WPTS to share its clock source. Once a master WPTS iselected, the other WPTSs in the group of WPTSs forming the virtual WPTSmay function as slaves. At 750, communication channels may beestablished among the elected master and all slaves that form thevirtual WPTS. Alternatively, communication channels may be establishedat an earlier point in the method than that depicted in FIG. 7. Forexample, communication channels may be established prior to orconcurrently with determining which clock source will be shared in 720.

At 760, the master WPTS may control calibration of the WPTSs forming thevirtual WPTS using the established communication channels. Duringcalibration, a phase offset associated with each WPTS may be determinedto synchronize transmissions across the WPTSs forming the virtual WPTS.In this way, the multiple WPTSs that may be spatially dispersed maywirelessly transmit power in a coordinated fashion to operate as asingle, virtual WPTS where transmissions from all WPTSs substantiallyconstructively interfere at a location of a WPRC.

At 770, the master WPTS may decide which WPRCs get wireless power andwhen the WPRCs get power. Here, apportioning of the available wirelesspower transmission capabilities of the virtual WPTS may take place. Theavailable wireless power transmission capabilities may be scheduled tooptimally supply power to WPRCs paired with the virtual WPTS based on,among other things, the demands of the respective WPRCs and the abilityof the WPTSs forming the virtual WPTS to meet the demands. At 780, allWPTSs forming the virtual WPTS provide wireless power to the pairedWPRCs in accordance with the decisions made at 770.

As wireless environment conditions change, such as a WPRC moves locationor perhaps an object moves into the environment which impairs orenhances a WPTS's ability to provide wireless power to a WPRC, thevirtual WPTS may need to be disbanded to form a more optimal virtualWPTS for the new environment. Thus, at 790, a determination may be madewhen the virtual WPTS should be disbanded and then the virtual WPTS maybe disbanded. The master WPTS, for example, may be responsible formaking said determination and for signaling to the slave WPTSs todisband. The determination may be made based on, for example, a changein one or more reception characteristics of a beacon from a paired WPRC.By way of example, a person may have moved into the line of sight of oneof the WPTSs and a paired WPRC blocking this direct path. The blockedWPTS may signal the updated condition to the master WPTS, and the masterWPTS may determine to disband the virtual WPTS such that the blockedWPTS is removed from the virtual WPTS. Additionally or alternatively,the virtual WPTS may not be fully disbanded but rather may be updated toremove the blocked WPTS only or the virtual WPTS may be fully disbandedand the method 700 may start over at 710 to determine which WPTSs shouldcollaborate to form a new virtual WPTS.

It should be noted that the example method and particular order of stepsdepicted in FIG. 7 is not meant to be limiting. The steps as depicted inFIG. 7 may be rearranged, combined, omitted, sub-divided, or otherwisemodified and still fall within the scope of the embodiments describedherein.

The following description provides details for calibrating an antennafor synchronized wireless power transmission with other antennas in thesystem to compensate for differences in phases of local clocks. Bycalibrating a phase offsets for each antenna, the system can ensure thatsignals constructively interfere at a location of a paired WPRC. Formore details on embodiments of performing said calibration acrossantennas within a WPTS, please refer to U.S. patent application Ser. No.15/596,661 filed May 16, 2017 and titled, “TECHNIQUES FOR CALIBRATINGWIRELESS POWER TRANSMISSION SYSTEMS FOR OPERATION IN MULTIPATH WIRELESSPOWER DELIVERY ENVIRONMENTS”, the contents of which are herebyincorporated by reference herein.

FIG. 8 is a diagram depicting an example system 800 for calibrating anantenna for synchronized transmission with other antennas in the system.FIG. 8 depicts a calibration unit 810, Cal. unit, including a localoscillator, LO, cal, coupled a respective antenna. FIG. 8 furtherdepicts a reference unit 820, Ref. ant., including a local oscillator,LO, ref, a respective phase invertor, and a respective antenna. FIG. 8further depicts a device under test 830, #n ant., including a localoscillator, LO, n, a respective phase invertor, and a respectiveantenna. The local oscillators may act as a clock source for therespective devices. Respective transmissions from the depicted devicesare based on the phases of the respective local oscillators, or clocksources, of the depicted devices. FIG. 8 further depicts various signalstransmitted to and from calibration unit 80, reference unit 820, anddevice under test 830 along with phases introduced by their respectivelocal oscillators. By calibrating transmissions from the device undertest 830 so that the phase shift introduced by its local oscillatormatches that of the reference unit 820, the system may achievesynchronized transmissions across the reference unit 820 and the deviceunder test 830.

The calibration unit 810 may send a transmission that is received by thereference unit 820 and the device under test 830, respectively. Thetransmission, when received at the reference unit 820, may include aphase shift of φ_(B,ref). The transmission, when received at the deviceunder test 830, may include a phase shift of φ_(B,n). A phase of thereceived transmission at the reference unit 820 with respect to itslocal oscillator may be expressed as φ_(B,ref)−φ_(LO,ref). A phase ofthe received transmission at the device under test 830 with respect toits local oscillator may be expressed as φ_(B,n)−φ_(LO,n). These signalsmay then be inverted and transmitted back to the calibration unit 810,again based upon a respective phase of their respective localoscillators. Thus, reference unit 820 may transmit a signal with a phaseshift of −φ_(B,ref)+2φ_(LO,ref) and device under test 830 may transmit asignal with a phase shift of −φ_(B,n)+2φ_(LO,n). The transmission fromreference unit 820, when received at the calibration unit 810, may theninclude another phase shift of φ_(B,ref) added to the−φ_(B,ref)+2φ_(LO,ref), which results in a received transmission with aphase shift of 2φ_(LO,ref). The transmission from device under test 830,when received at the calibration unit 810, may then include anotherphase shift of φ_(B,n) added to the −φ_(B,n)+2φ_(LO,n), which results ina received signal with a phase shift of 2φLO,n. Through this round-triptransmission between the calibration unit 810 and the reference unit820, as well as the round-trip transmission between the calibration unit810 and the device under test 830, the calibration unit is able togather enough information to determine the phase shifts introduced bythe respective oscillators, or clock sources, of the reference unit 820and the device under test 830, since it now received transmissions withknown relationships to the phase shift introduced by respective localoscillators. The calibration unit 810 may then provide clock signalinformation to the device under test 830 so that the device under testmay adjust its oscillator, or clock, phase by +2(φ_(LO,ref)−φ_(LO,n)) sothat signals transmitted by the device under test 830 are aligned withsignals transmitted from the reference unit 820.

The above described calibration with respect to FIG. 8 may be applied toany antenna within a multiple WPTS system. Within a single WPTS, acalibration may be needed across all antennas and their respective localoscillators to properly compensate phase shifts per antenna. In thisexample scenario, an antenna of the WPTS may be designated as areference antenna, and the remaining antennas may be designated as adevice under test that are each calibrated with respect to the referenceantenna. In this example, the calibration unit may be another WPTS, aWPRC, or a calibration unit specifically designed for calibrationpurposes.

As described herein, to form a virtual WPTS, there may be a need tocalibrate transmissions across all WPTSs that form the virtual WPTS. Forexample, there may be a need to calibrate transmissions from antennas ofa second WPTS with respect to a first WPTS. In this example scenario,the calibration depicted in FIG. 8 and described above may be applied.For two WPTSs, a calibration of clock phases of all antennas within thefirst WPTS may be done with respect to the clock of its referenceantenna. Similarly, a separate calibration of each clock coupled to eachantenna within the second WPTS may be done with respect to the clock ofits reference antenna as well. Additionally, the reference antenna ofthe second WPTS may be calibrated with respect to the reference antennaof the first WPTS in accordance with FIG. 8. For example, the referenceantenna of the second WPTS may be the device under test 830 and thereference antenna of the first WPTS may be the reference unit 820 asshown in FIG. 8. As a result, the clocks of the second WPTS may beoffset such that transmissions from the second WPTS may be aligned withtransmissions from the first WPTS. Thus, the system need not explicitlycalibrate all antennas from the second WPTS with respect to the firstWPTS, but may effectively achieve calibration across all antennas ofboth WPTSs by calibrating the reference antenna of the second WPTS withrespect to the first WPTS. Thus, as depicted in FIGS. 5-7 and asdescribed in their associated descriptions, the local oscillators, orclock sources, of all WPTSs that form a virtual WPTS may be calibratedand clock signal information may be shared among the WPTSs.

FIG. 9 is a signal flow diagram 900 depicting an example systemincluding two WPTSs, WPTS 1 and WPTS 2, that may be calibrated to act asa virtual WPTS to provide wireless power to a WPRC. In this examplesystem, the WPTS 1 may act as a master WPTS and may further act as acalibration unit 810 as well as reference unit 820 such as that depictedin FIG. 8. For example, transmissions from one or more antennas of WPTS1 may act as calibration unit antennas and may be received by anotherantenna that may act as a reference antenna included in WPTS 1. Thereference antenna included in WPTS 1 may transmit signals back to theone or more calibration unit antennas included in WPTS 1. A referenceantenna included in WPTS 2 may act as a device under test such as deviceunder test 830 depicted in FIG. 8. The reference antenna from WPTS 2 mayalso receive transmissions from the one or more calibration unitantennas included in WPTS 1 and may transmit signals back to the one ormore calibration unit antennas included in WPTS 1. As described abovewith respect to FIG. 8, WPTS 1 may then be able to supply clockinformation to WPTS 2 so that it may adjust a phase offset of itsreference antenna to align transmissions with those of WPTS 1.

As depicted in FIG. 9, at 905 a master WPTS is selected. In the exampledepicted in FIG. 9, WPTS 1 may be selected as the master. At 910, theone or more antennas acting as calibration unit antennas may transmit abeacon that may be received by an antenna chosen as a reference antennaof WPTS 2 and by an antenna chosen as a reference antenna of WPTS 1.Each reference antenna may detect a received phase at 911 and 912,respectively. At 920, WPTS 2 may transmit an indication of the phasedetected at its reference antenna back to WPTS 1. At 925, WPTS 1 maysave an indication of the detected phase. At 925, WPTS 1, which mayinclude both its reference antenna and the one or more calibration unitantennas, may also save the phase detected by its reference antenna fromthe transmission from the one or more calibration unit antennas.

At 930, WPTS 1 may direct WPTS 2 to send transmissions via its referenceantenna at sequential phases. At 935, WPTS 2 may transmit signals withsequentially incremented or decremented phase shifts. For example, aphase shift of the local oscillator associated with the referenceantenna of WPTS 2 may be incremented or decremented sequentially andcorresponding transmissions using the different phase shifts may betransmitted by the reference antenna of WPTS 2. These sequentialtransmissions may be received by the one or more calibration unitantennas of WPTS 1. Concurrently, a reference antenna of WPTS 1 maytransmit a signal that is received by the one or more calibration unitantennas of WPTS 1. As the sequential transmissions from the referenceantenna of WPTS 2 and the concurrent transmissions from the referenceantenna of WPTS 1 are received by the one or more calibration unitantennas of WPTS 1, at 940 a sum received power from both of thereference antennas is determined. At 940, as the phase shift isincremented or decremented throughout the sequential transmissions fromthe reference antenna of WPTS 2, a received power level is determinedfor each of the sequential transmissions. A peak received power at theone or more calibration unit antennas may correspond to a particulartransmission selected from the sequential transmissions wherein a phaseshift of the selected transmission from the reference antenna of WPTS 2is substantially calibrated with a phase of the transmission from thereference antenna of WPTS 1. At 945, the phase shift that corresponds tothe peak power is determined.

At 950, WPTS 1 shares an indication of the calibration phase shift thatcorresponds to the peak power with WPTS 2. At 960, WPTS 1 and WPTS 2 mayact as a virtual WPTS and may concurrently send calibrated transmissionsto the WPRC. At 961, WPTS 1 may directionally transmit power to the WPRCwhile, at 962, WPTS 2 may concurrently and directionally transmit powerusing the indication of the calibration phase shift so thattransmissions from WPTS 2 constructively interfere with transmissionsfrom WPTS 1 at a location of the WPRC.

FIG. 10 is a signal flow diagram 1000 depicting another example systemincluding two WPTSs, WPTS 1 and WPTS 2, that are calibrated to act as avirtual WPTS to provide wireless power to a WPRC. In this examplesystem, the WPTS 1 may act as a master WPTS and a reference unit 820such as that depicted in FIG. 8. The WPRC may act as a calibration unitsuch as calibration unit 810 depicted in FIG. 8. WPTS 2 may act as adevice under test such as device under test 830 depicted in FIG. 8. Forexample, transmissions from one or more calibration unit antennasincluded in WPRC may be received by a reference antenna included inWPTS 1. The antenna acting as the reference antenna included in WPTS 1may transmit signals back to the one or more calibration unit antennasincluded in the WPRC. The reference antenna included in WPTS 2 may alsoreceive transmissions from the one or more calibration unit antennasincluded in the WPRC and may transmit signals back to the one or morecalibration unit antennas included in the WPRC. As described above withrespect to FIG. 8, WPTS 1 may then be able to supply clock informationto WPTS 2 so that it may adjust a phase offset of its reference antennato align transmissions with those of WPTS 1. Although FIG. 10 depicts aWPRC, a dedicated calibration unit or another WPTS may be used in placeof the WPRC to perform the depicted calibration processes.

As depicted in FIG. 10, at 1001 a master WPTS is selected. In theexample depicted in FIG. 10, WPTS 1 may be selected as the master. At1005, the WPRC may transmit a beacon that may be received by a referenceantenna of WPTS 2 and by a reference antenna of WPTS 1. Each referenceantenna may detect a received phase at 1011 and 1012, respectively. At1015, WPTS 2 may transmit an indication of the phase detected at itsreference antenna back to WPTS 1. At 1020, WPTS 1 may save indicationsof the detected phases from 1011 and 1012.

At 1025, WPTS 1 may direct WPTS 2 to send transmissions via itsreference antenna at sequential phases. At 1035, WPTS 2 may transmitsignals with sequentially incremented or decremented phase shifts. Forexample, a phase shift of the local oscillator associated with thereference antenna of WPTS 2 may be incremented or decrementedsequentially and corresponding transmissions using the different phaseshifts may be transmitted by the reference antenna of WPTS 2. Thesesequential transmissions may be received by the WPRC. Concurrently, at1030, a reference antenna of WPTS 1 may transmit a signal with a phasebased on the received beacon from the WPRC. As the sequentialtransmissions 1035 from the reference antenna of WPTS 2 and theconcurrent transmissions 1030 from the reference antenna of WPTS 1 arereceived by the WPRC, at 1040 a sum received power from thetransmissions from both of the reference antennas is determined. At1040, as the phase shift is incremented or decremented throughout thesequential transmissions from the reference antenna of WPTS 2, areceived power level is determined for each of the sequentialtransmissions. A peak received power at the WPRC may correspond to aparticular transmission selected from the sequential transmissions 1035wherein a phase shift of the selected transmission from the referenceantenna of WPTS 2 is substantially calibrated with a phase of thetransmission from the reference antenna of WPTS 1. At 1045, anindication of the received power data is transmitted from the WPRC toWPTS 1. At 1050, the phase shift that corresponds to the peak power isdetermined.

At 1055, WPTS 1 shares an indication of the calibration phase shift thatcorresponds to the peak power with WPTS 2. At 1060, WPTS 1 and WPTS 2may act as a virtual WPTS and may concurrently send calibratedtransmissions to the WPRC. At 1061, WPTS 1 may directionally transmitpower to the WPRC while at 1062 WPTS 2 may concurrently anddirectionally transmit power using the indication of the calibrationphase shift so that transmissions from WPTS 2 constructively interferewith transmissions from WPTS 1 at a location of the WPRC.

Again, as referenced above, the WPRC depicted in FIG. 10 mayalternatively be a dedicated calibration unit or another WPTS forpurposes of calibration. Once calibration is successfully achieved, WPTS1 and WPTS 2 may form a virtual WPTS that may wireless transmit power toa WPRC in an optimal fashion.

Although two WPTSs and a WPRC are depicted in FIGS. 9 and 10, any numberof WPTS may be used. Moreover, as referenced above, a separatecalibration unit may be used to calibrate WPTS 1 and WPTS 2. A separatecalibration unit need not be collocated with WPTS 1, WPTS 2, or theWPRC.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a WPTS or WPRC.

What is claimed is:
 1. A method performed by a wireless powertransmission system (WPTS), the method comprising: receiving aninstruction to group with one or more WPTSs to collaborate to transmitwireless power to a wireless power receiver client (WPRC), wherein theinstruction is based on a location of the WPRC, a power demand of theWPRC for an amount of power, and an ability of the WPTS and a respectiveability of each of the one or more WPTSs to contribute to fulfilling thepower demand of the WPRC for the amount of power, wherein the respectiveability of each of the one or more WPTSs is based at least in part on aremaining amount of available power beyond a power load level providedby the respective WPTS to at least one other WPRC; receiving anindication of a clock; adjusting a phase offset of a local oscillatorbased on the indication of the clock; and providing wireless power tothe WPRC in collaboration with the one or more WPTSs, wherein thewireless power is transmitted based on the adjusted phase offset.
 2. Themethod of claim 1, further comprising forming a virtual WPTS with theone or more WPTS.
 3. The method of claim 1, further comprising the WPTStransmitting sequential transmissions each with a respective incrementedphase shift to determine the adjusted phase offset that aligns withtransmissions from the one or more WPTSs.
 4. The method of claim 2,further comprising receiving an instruction to disband the virtual WPTSon a condition that the WPRC has moved away from at least one of theWPTSs of the one or more WPTSs.
 5. The method of claim 1, wherein theindication of a clock indicates a clock from a plurality of clocksources to use as a common clock.
 6. The method of claim 5, wherein theindication of a clock indicates a central controller board clock source.7. The method of claim 1, wherein the WPTS is a slave WPTS and theinstruction is received from an elected master WPTS.
 8. The method ofclaim 7, wherein the WPTS and the one or more WPTSs are calibrated withone another to align transmissions based on respective clocks.
 9. Themethod of claim 8, wherein the wireless power provided by the WPTSsubstantially constructively interferes at the WPRC with wireless powertransmitted by the one or more WPTSs.
 10. The method of claim 9, whereinthe received indication of the clock is based on a power received at acalibration unit.
 11. A wireless power transmission system (WPTS)comprising: a receiver configured to: receive an instruction to groupwith one or more WPTSs to collaborate to transmit wireless power to awireless power receiver client (WPRC), wherein the instruction is basedon a location of the WPRC, a power demand of the WPRC for an amount ofpower, and an ability of the WPTS and a respective ability of each ofthe one or more WPTSs to contribute to fulfilling the power demand ofthe WPRC for the amount of power, wherein the respective ability of eachof the one or more WPTSs is based at least in part on a remaining amountof available power beyond a power load level provided by the respectiveWPTS to at least one other WPRC; and receive an indication of a clock; alocal oscillator configured to adjust its phase offset based on theindication of the clock; and a transmitter configured to providewireless power to the WPRC in collaboration with the one or more WPTSs,wherein the wireless power is transmitted based on the adjusted phaseoffset.
 12. The WPTS of claim 11, wherein the WPTS forms a virtual WPTSwith the one or more WPTSs.
 13. The WPTS of claim 11, wherein thetransmitter is further configured to transmit sequential transmissionseach with a respective incremented phase shift to determine the adjustedphase offset that aligns with transmissions from the one or more WPTSs.14. The WPTS of claim 12, wherein the receiver is further configured toreceive an instruction to disband the virtual WPTS on a condition thatthe WPRC has moved away from at least one of the WPTSs of the one ormore WPTSs.
 15. The WPTS of claim 11, wherein the indication of a clockindicates a clock from a plurality of clock sources to use as a commonclock.
 16. The WPTS of claim 15, wherein the indication of a clockindicates a central controller board clock source.
 17. The WPTS of claim11, wherein the WPTS is a slave WPTS and the instruction is receivedfrom an elected master WPTS.
 18. The WPTS of claim 17, wherein the WPTSand the one or more WPTSs are calibrated with one another to aligntransmissions based on respective clocks.
 19. The WPTS of claim 18,wherein the wireless power provided by the WPTS substantiallyconstructively interferes at the WPRC with wireless power transmitted bythe one or more WPTSs.
 20. The WPTS of claim 19, wherein the receivedindication of the clock is based on a power received at a calibrationunit.